DETROIT, MI -- The PBS' "History Detectives" has plans July 22 to take a in-depth look at the mysterious 1975 disappearance of Teamster boss Jimmy Hoffa.

This show, in its 11th season, will air at 9 p.m. on Detroit Public TV (Channel 56 for most viewers). For more information, visit the station's website.

Hoffa, a Brazil, Ind. native, moved with his family to Detroit in 1924 and was declared dead on July 30, 1982. He was 62 at the time of his disappearance.

Hoffa, at the time, was one of the most powerful men in the country because of his union leadership.

Many working Americans considered Hoffa their hero because of his efforts to improve working conditions for them, but he also had powerful enemies

For decades, investigators have searched for clues about his disappearance.

The clues, however, have been few and far between.

After serving prison time for conspiracy and fraud, Hoffa was pardoned by President Richard Nixon.

Since so many questions remain about Hoffa's life and death, "History Detectives" vows to take a close look at several angles.

This from the "History Detectives" website about the Hoffa episode:

"Recently declassified government files reveal shocking evidence of corruption at the highest levels. Interviews with a former mob lawyer, a murder witness, and an FBI agent are among the sources History Detectives unearth as they track Jimmy Hoffa’s final hours and answer the question: “Who killed Jimmy Hoffa?”